Conventionally, refrigeration systems have been known which are utilized for freight containers or other purposes and cool the inside of such containers.
For example, a refrigeration system disclosed in Patent Document 1 includes a refrigerant circuit for cooling the inside of a container. This refrigerant circuit is connected with a compressor, a condenser, an electronic expansion valve, and an evaporator in this order. The condenser is placed outside the container. A condenser fan is placed in the vicinity of the condenser. On the other hand, the evaporator is placed inside the container. An evaporator fan is placed in the vicinity of the evaporator. The degree of opening of the electronic expansion valve is controlled to maintain the degree of superheat of refrigerant at the evaporator side within a predetermined range.
During, for example, chilling operation of this refrigeration system, the condenser fan, the evaporator fan and the compressor are operated. When refrigerant compressed by the compressor is delivered to the condenser, the condenser is operated in the following manner: Heat is exchanged between an outdoor air delivered by the condenser fan and the refrigerant, and then the refrigerant releases heat to the outdoor air and is condensed. Thereafter, the refrigerant is reduced in pressure by the electronic expansion valve and then flows into the evaporator. In the evaporator, heat is exchanged between an indoor air delivered by the evaporator fan and the refrigerant, and the refrigerant absorbs heat from the indoor air and evaporates. As a result, the indoor air in the container is cooled. The refrigerant that has evaporated in the evaporator is sucked into the compressor and again compressed.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-327964